1. Field of the Invention
The present invention relates to computer systems that include field-replaceable units (FRUs).
2. Related Art
Every computer includes both hardware and software. The hardware of a computer includes electromechanical components such as microprocessors, buses, input/output (I/O) controllers, memory, and mass storage devices (such as hard disk drives). It can be difficult to maintain and repair such components, particularly as they become more and more complex and miniaturized. Increasingly, it is not feasible to attempt to perform an electrical or mechanical repair on a component such as a bus or I/O controller. Rather, often the best that a technician faced with a malfunctioning computer can do is to identify the component that is the source of the problem and to physically replace the identified component with a new component. Such a repair process can be tedious, time-consuming, and costly because it requires a human technician to diagnose the cause of the malfunction, open the computer housing, physically remove (and possibly dispose of) the malfunctioning component, and physically install the new component. Although the process of diagnosing computer malfunctions is becoming increasingly automated, the component replacement process must still be performed manually.
In early computer systems it was often difficult or impossible to replace certain hardware components—such as the central processing unit (CPU), memory, and I/O controllers—after the computer had been manufactured. Such components might, for example, be hardwired together, in which case attempting to remove any of such components might irreversible damage the computer. In some cases, it might be possible to remove such components by breaking and re-establishing physical connections by soldering or using some other tedious and time-consuming process requiring a skilled technician to perform.
Computer hardware designers are increasingly designing computer systems so that components (such as the CPU, memory, and I/O controllers) can be replaced easily in the field (i.e., at user locations). A component that can be easily removed from a computer and replaced with a new component in the field is referred to as a “field-replaceable unit” (FRU). Modern computers increasingly include modular hardware interfaces which allow FRUs to be removed easily by a relatively unskilled technician. Removing an FRU may, for example, only require removing a few screws and pulling the FRU out of the computer. The same technician may then install a replacement FRU with the same ease. Although the use of FRUs decreases the difficulty, cost, and time required to replace a hardware component, field-replacement of FRUs still requires a human technician to remove and replace the defective FRU.
Software, in contrast, is embodied in the form of electromagnetic signals stored in a mass storage device (e.g., a hard disk drive) or other form of electronic memory. It has therefore traditionally been possible to replace or update faulty or outdated software merely by erasing the old software and replacing it with new software provided on a tangible storage medium, such as a floppy diskette or CD-ROM. Updating or replacing software, therefore, traditionally has been significantly easier and less costly to perform than hardware replacement. The widespread use of computer networks and the Internet has further simplified the process of updating software by making it possible to download software over a network and install it—in some cases without any human intervention—without the need to distribute the software on a physical medium such as a floppy diskette.
There is now a trend in computer hardware design to implement various hardware components in ways that make it possible for hardware to be updated and effectively replaced in a manner that is similar to the manner in which it traditionally has been possible to update and replace software. The term “field-programmable unit” (FPU) refers to a hardware component whose functionality may be modified by electronically programming it. Examples of FPUs include system firmware (e.g., BIOS), embedded enclosure process firmware, and Field-Programmable Gate Arrays (FPGAs). Each of these kinds of FPUs is capable of storing electrical signals representing code that dictates, in whole or in part, the functions performed by the FPU. The functionality of an FPU, therefore, may be modified merely by modifying the code (in the form of electrical signals) stored in the FPU.
It may be necessary or desirable to re-program an FPU in any of a variety of circumstances. For example, the code stored in an FPU may become out-of-date, in which case it may be desirable to update the code in the FPU to enable it to perform new functions. As another example, the code stored in a newly-installed FPU may be incompatible with other hardware in the system, in which case it may be necessary to update the FPU's code with code that is compatible with the other hardware in the system. The code in an FPU may also become corrupted, in which case it may be necessary to re-load fresh code into the FPU to restore it to a functional state.
In all of these cases, the primary advantage of the FPU over conventional forms of hardware is that the FPU may be repaired or effectively replaced merely by storing new code in the FPU. New code may be stored in an FPU using a process that is similar to the process by which software is updated. For example, a human technician may provide the code to the computer using a floppy diskette or by downloading the code over a network. The technician may then instruct the computer to store the new code in the FPU, a process which may typically be performed quickly and without requiring the technician to open the computer housing or perform any physical modifications to the computer. Repairing an FPU can therefore be significantly less tedious, time-consuming and expensive than repairing a conventional hardware component.
Although an FRU (field-replaceable unit) need not be field-programmable, an FRU may include one or more FPUs (field-programmable units). An FRU may therefore be field-programmable as well as field-replaceable. In a particular computer system, it is possible for the FPU code stored in an FRU to be incompatible with other FPU code in the system or with hardware components of the system. Such incompatibilities may cause the system to malfunction. It is desirable to avoid such incompatibilities to maintain proper system function.